1. Field of the Invention
This invention is related to an improvement in the structure of a screw and in particular to one which can be easily turned into a piece hard wood.
2. Description of the Prior Art
The conventional screw consists essentially of a solid cylinder, usually of metal, around which a thread winds spirally, either clockwise or counterclockwise. However, it is difficult to turn the screw into an object if it is made of hard wood. Hence, an improved screw (see FIG. 1) has been designed to obviate this drawback. As shown, the screw includes a shank 1 formed with spiral circular threads 11 at the upper portion thereof. The spiral circular threads 11 at the lower portion of the shank 1 are provided with a plurality of teeth 12 for facilitating the tuning of the screw into the wood. Nevertheless, although the teeth 12 enables the screw to turn into a piece of hard wood, it still requires a lot of effort to turn the screw thereby often making one feel utterly exhausted in order to fasten pieces of hard wood.
Therefore, it is an object of the present invention to provide an improvement in the structure of a screw which can obviate and mitigate the above-mentioned drawbacks.